The hypothesis underlying this proposal is that cytokines derived from platelets, glomerular endothelial cells, and macrophages regulate glomerular mesangial and endothelial cell proliferation and matrix production. The overexpression of these cellular functions may lead to the development glomerular sclerosis. It is postulated that two likely mediators involved in the process of glomerular sclerosis are platelet derived growth factor and transforming growth factor beta, both platelet products which may also be synthesized by glomerular endothelial cells. Methods were developed in the past 12 months which allow routine culture of bovine glomerular endothelial cells. Therefore, the influence of cytokines on glomerular endothelial and mesangial cells in vitro can be determined, and the role of glomerular endothelial cell-derived mediators on glomerular mesangial cell function can be examined. The proposed studies will delineate glomerular endothelial cell and mesangial cell proliferation, matrix synthesis, and other functions in response to a number of known polypeptide cytokines. Studies will involve the determination of DNA synthesis, cell number as a function of time, and the quantification of collagen, matrix proteoglycan add fibronectin synthesis. The question whether platelet derived growth factor and transforming growth factor beta modulate glomerular cell growth and matrix synthesis will receive particular attention. Using gel filtration chromatography, enzyme susceptibility profiles, radioligand binding inhibition studies, neutralizing antibody studies and Western blotting techniques, the proposal furthermore seeks to define the identity of mitogenic and anti-proliferative mediators released by glomerular endothelial cells. Finally, in co-culture systems it will determined whether specific mediators released by glomerular endothelial cells in fact regulate mesangial cell proliferation and matrix synthesis. These studies will identify possible mediators that may alter glomerular mesangial cell and endothelial cell functions to produce glomerular sclerosis in vivo.